Track circuit system



Feb. 27, 1934. w s o 1,949,194

TRACK CIRCUIT SYSTEM Original Filed March 3, 1927 INVENTOR.

A W/H/ imson 1% ATTORNEY.

' Fatented Feb. 27, 1 934 UNlT FICE mesne assignments, to The Union Switch 8; Signal Company, Swissvale, Pa, a corporation of Pennsylvania Original application March 3, 1927, Serial No.

172,325, new Eatent No. 1,791,780, dated February 10, 1931. Divided and this application January 14, 1931. Serial No. 508,618

10 Claims.

This invention relates to track circuit systems and particularly to systems in which periodic current is supplied to the traclaway through a transformer or similar device employing a magnetizable core the permeability of which is varied to control the current supplied to the trackway.

The present case is a division of my copending application Serial No. 172,325, filed March 3, 1927, for Train control systems which application has matured into Patent No. 1,791,780, dated February 10, 1931.

The accompanying drawing is a diagrammatic view showing one form of track circuit system embodying my invention.

In this invention it is proposed to make use of the fact that the wave form of a single-frequency alternating current can be made non-sinusoidal; that is: the alternating current can be so modified that the momentary values or" a compound resultant wave do not vary in accordance with a pure sine law, but has momentary values which are the summation of the sine functions or the waves of several components, The sine function possessing the lowest frequency is called the first harmonic component or the fundamental, and all the other sine functions, whose frequencies are multiples of that of the fundamental, are called higher or upper harmonic components.

One trackway arrangement embodying the invention is shown in the accompanying drawing, in which the reference characters 1 and 2 designate the traffic rails of a stretch of railway track over which tramc moves in the direction indicated by the arrow. The rails ,1 and 2 are preferably arranged in blocks A, B and C by means of insulated joints 3 or otherwise. Current is supplied to the rails of each block from a trans former designated by the reference character T with a suitable distinguishing subscript. Each transformer T comprises a magnetizable core 6 provided with a primary 5 and a secondary 4. The primary 5 of each transformer T is constantly supplied with single frequency periodic current from a suitable source, such as an alternator G, over line wires 12 and 13, and the secondary 4 of each transformer T is connected across the traffic rails adjacent one end of the corresponding block.

In addition, each block is provided a tracl: relay, designated by the reference character B with a subscript corresponding to the location, and connected across the rails of the associated block.

The permeability of the core of each transformer T is controlled by traffic conditions in advance. Referring particularly to transformer Tb, for example, the core 6 of this transformer carries a coil 250, and this coil is energized by battery 251 by means of a circuit which is closed when track relay Rn of the block in advance is energized. When 250 energizes the core of Tb, the material of the core is worked at a point well up on its magnetization curve and its permeability is comparatively low. As a result, during half cycles of one polarity of the alternating current supplied to the primary 5, the induction will increase but slightly, while during half cycles of the other polarity, the decrease will be relatively large. This uneven change in the induction of the iron core will produce a wave form in the current of secondary 4-. which will have a pronounced third harmonic component as well as a pronounced first harmonic or fundamental component. When relay Ra is deenergized and coil 250 is deenergized, the permeability of core 6 is increased, and the core is then worked at a point well down below the knee of the magnetization curve, and the third harmonic is suppressed.

The result of the arrangement above described is that when block A is unoccupied, so that relay Ra is energized, transformer Tb supplies block B with current of the fundamental frequency having a pronounced third harmonic, but when relay 86 Rb is deenergized, as by the presence of a train in block A, the current supplied to block B is substantially without a third harmonic component.

It will be understood, of course, that each block is provided with apparatus similar to that 90 here described in connection with block B.

The current supplied to the trackway in accordance with my invention may be employed in any suitable manner. For example, in my copending application, Serial No. 172,325, of which this case is a division, I have disclosed train carried apparatus selectively responsive to current in the trackway and suitable for use with the trackway circuits here shown to give one indication when 10 the trackway is supplied with current of a fundamental frequency having a pronounced third A harmonic and a different indication when the trackway current does not include such harmonic component. 108

Although I have herein shown and described only one form of track circuit system embodying my invention, it is understood that various changes and modifications may be made therein within the scope of the appended claims without 110 departing from the spirit and scope of my invention.

Having thus described my invention, what I claim is:

1. In combination with a stretch of traffic track, means including a transformer having a magnetizable core for supplying periodic current to the rails of said stretch, and means controlled by traffic conditions for at times supplying flux to said core to control the current supplied by said transformer to said rails.

2. In combination with a stretch of traffic track, means including a transformer having a magnetizable core for supplying periodic current to the rails of said stretch, a coil inductively related with said core, and means controlled by traific conditions for supplying current to said coil to control the current supplied by said transformer to said rails.

3. In combination with a stretch of traific track, a transformer having a magnetizable core, a primary supplied with periodic current and inductively related with said core, a secondary inductively related with said core and connected with the rails of said stretch, a coil inductively related with said core, and means controlled by traflic conditions for at times supplying unidirectional current to said coil to control the current supplied to said rails from said secondary.

4. In combination, two adjacent blocks of traffic track, a track relay responsive to traific conditions in one block, a transformer having a magnetizable core carrying a primary and a secondary, means for supplying periodic current to said primary, means for supplying current from said secondary to the track rails of the other said block, a coil inductively related with said core, and means controlled by said track relay for at times supplying direct current to said coil to control the current supplied by said secondary to said other block.

5. In combination, two adjacent blocks of traffic track, a track relay responsive to trafiic conditions in one block, a transformer having a magnetizable core carrying a primary and a secondary, means for supplying periodic current to said primary, means for supplying current from said secondary to the rails of the other said block, a coil inductively related with said core, andmeans controlled by said track relay for at times supplying current to said coil to cause changes in the magnetization of said core independently of current in said primary.

6. In combination with a stretch of trafllc track, means including a transformer having a magnetizable core for supplying periodic current to the rails of said stretch, and means for so varying the permeability of said core as to cause the transformer to supply to the rails an indication current different from that otherwise flowing.

7. In combination with a stretch of traffic track, means including a transformer having a magnetizable core for supplying periodic current to the rails of said stretch, and means for at times so supplying flux to said core as to cause the transformer to supply to the rails an indication current different from that otherwise flowing.

8. In combination with a stretch of traffic track, means including a transformer having a magneiizable core for supplying periodic current to the rails or" said stretch, and a coil, inductively related to said core, which when energized so varies the permeability of said core as to cause the transformer to supply to the rails an indication current difierent from that otherwise flowing.

9. In combination with a stretch of trafiic track, a transformer having a magnetizable core, a primary supplied with periodic current and inductively related to said core, a secondary inductively related to said core and connected with the rails of said stretch, and a coil, inductively related to said core, which when energized controls thc current supplied by said secondary to said rails.

10. In combination with a traific track, means including a transformer, having a magnetizable core, for supplying a single-frequency alternating current of a given fundamental to the rails of said stretch, and means for so varying the permeability of said core as to modify the current supplied to the rails by the transformer to include a pronounced harmonic component higher than the fundamental.

ARBA G. WILLIAMSON. 

